Critical Boundary Conditions for the Effective String

TL;DR

This paper explores how boundary conditions in gauge systems influence the effective string description, revealing a universal free fermion string behavior with specific boundary phases and predicting a universal flux tube thickness.

Contribution

It introduces a boundary condition framework that transforms the effective string into a universal free fermion string with a boundary phase nu=1/4, aligning with previous lattice data models.

Findings

Universal free fermion string behavior at quantum level

Boundary phase nu=1/4 confirmed

Predicts universal flux tube thickness

Abstract

Gauge systems in the confining phase induce constraints at the boundaries of the effective string, which rule out the ordinary bosonic string even with short distance modifications. Allowing topological excitations, corresponding to winding around the colour flux tube, produces at the quantum level a universal free fermion string with a boundary phase nu=1/4. This coincides with a model proposed some time ago in order to fit Monte Carlo data of 3D and 4D Lattice gauge systems better. A universal value of the thickness of the colour flux tube is predicted.